Cystic fibrosis (CF) is due to various defects in an apical epithelial Cl- channel, the cystic fibrosis transmembrane regulator (CFTR). The disease can usually be traced to a single point mutation in CFTR that renders it incapable of transfer to the outer membrane. One potential approach to managing the disease could be the artificial activation of Ca2+- dependent Cl- channels also abundant in epithelial cells. However, this speculative therapeutic pathway is currently ineffective because the cholinergic stimulation of intracellular Ca2+ is accompanied by a slow and prolonged increase in intracellular Ins(3,4,5,6)P4 (IP4) levels. The applicant has previously identified IP4 as an endogenous negative regulator of Ca2+-dependent Cl- transport in epithelial cells. In this study, a series of compounds with characteristics of IP4 antagonists will be tested to assess their potential use as treatments for CF. CTFR(-) epithelial cell mutants will be developed to determine if CFTR regulates the expression of elements involved in IP4-mediated inhibition of Cl- secretion. The IP4 antagonists will be tested in a non-transformed pancreatic cell line (PDEC) which has been shown to have a Ca2+-dependent Cl- conductance and in a CFTR(-) human cell line. The applicant will also determine the effects of the compounds on Cl- secretion in human airway epithelia derived from normal and CF patients. These studies will determine the range of tissues that would be appropriate targets for modulation by inositol polyphosphate derivatives and whether they will augment Cl- secretion in diseased as well as in normal epithelia.